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Интеллектуальная Система Тематического Исследования НАукометрических данных |
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Nonlinear-optical approaches for the THz wave detectionтезисы доклада
- Автор: Kitaeva G.Kh
- Сборник: EMN Meeting on Vacuum Electronics. Program&Abstract, Las Vegas, NV USA, November 21-24, 2015
- Тезисы
- Год издания: 2015
- Место издания: OAHOST Open-Access Publication and Conference Management by Scientists and for Scientists
- Первая страница: 29
- Последняя страница: 31
- Аннотация: Availability of portable high-sensitive terahertz-wave detectors plays a crucial role for successful implementation of various applications of the THz waves in spectroscopy, imaging, non-destructive evaluation and other areas. Among different approaches for compact table-top THz detectors, nonlinear-optical schemes are in the forefront now mostly due to the famous method of electro-optic (EO) sampling. Crystals of the zinc-blende symmetry are widely used for THz time-domain spectroscopic measurements under conditions of femtosecond-pulsed laser pumping of both the THz generator and the EO detector. A standard EO detection technique utilizes phase changes of polarization components of the laser radiation, which take place in the presence of a terahertz electric field in a EO crystal (usually, ZnTe). However, the use of crystals of other symmetry, such as DAST, Mg:LiNb03 and other ones with strong nonlinearity and high natural birefringence is hindered in the standard technique. In our works we have shown that such crystals can be used in a more simple “probe-energy” EO scheme, where the terahertz-induced parameter under measurement is an energy change of the transmitted probe pulse. By this way the narrow-band EO detection has been demonstrated in PPLN crystals for the first time. Recently, sensitivity of the “probe-energy” scheme was improved essentially, by more than two orders of magnitude, using the special spectral filtering of the optical pulses. Taking advantage of another approach, the quasi-CW nonlinear-optical terahertz detecting schemes utilize the processes of up-conversion of terahertz frequency to the optical range in non-linear optical crystals pumped by laser pulses of nanosecond duration. This method is suitable for an incoherent detection of THz wave intensity distributions and is free of any restrictions imposed by the mode of the THz wave generation. We propose to use the values of spectral brightness of classical thermal field fluctuations and the effective spectral brightness of quantum zero vacuum fluctuations at THz frequencies for calibration of the spectral sensitivity of such schemes. Fluctuation fields at idler (terahertz) frequencies cause noise signals at optical output frequencies in the nonlinear-optical parametric up-convertor. These signals appear in the anti-Stokes part of the spectrum due to sum-frequency generation process between thermal fluctuations and pump fields, and in the Stokes part of the spectrum due to difference-frequency generation and spontaneous parametric down-conversion of the pump radiation. Comparison between the signals detected in both parts of the spectrum, in absence and in presence of an external terahertz-wave radiation, enables to estimate the radiation spectral brightness and to determine an absolute value of brightness for thermal fluctuations.
- Добавил в систему: Китаева Галия Хасановна